(a) Field of the Invention
The present invention relates to a process for preparing thermoplastic transparent resin, more particularly to a process for preparing thermoplastic transparent resin having superior moisture, impact and heat resistance, natural color, and excellent transparency, which is prepared by blending transparent graft resin with methylmethacrylate-styrene-acrylonitrile (hereinafter referred to as “MSAN”) copolymer after preparing the former through emulsion polymerization and the latter through bulk polymerization.
(b) Description of the Related Art
Recently, studies for providing materials used with high functionalities such as transparency, etc. have been strongly and actively pursued in order to promote differentiation of product models as industries advance, and technology continues to change our lives.
For example, studies for newly providing transparency to materials such as transparent windows of personnel communication systems, covers of washing machines through which machine contents can be seen, monitor housings through which internal components of computer monitors can be seen, game machine housings, transparent windows of home appliances and office appliances, etc. are intensively being pursued.
However, although acrylonitrile-butadiene-styrene (hereinafter referred to as “ABS”) copolymer resin used in these conventional components is superior in terms of qualities such as impact resistance, chemical resistance, processibility, surface glossiness, etc., it is limited in application to materials in which transparency is required since it is an opaque material because of the nature of the resin.
The conventional technologies for providing plastic materials with transparency include 1) a method using transparent polycarbonate resin; 2) a method for providing transparent polymethyl methacrylate (PMMA) resin with impact resistance (U.S. Pat. No. 3,787,522); and 3) a method for providing high impact polystyrene (HIPS) resin with transparency (European Patent No. 703,252A2 and Japanese Patent Laid-open Publication No. Heisei 11-147920).
However, the method 1) has problems of low chemical resistance and impact resistance at a low temperature, and it is short in processibility hereby limiting application with large scale components, although ransparency and impact resistance at ordinary temperature are superior. The method 2) has an extremely lower impact resistance and a lower chemical resistance thus limiting applications, although transparency and processibility are superior. The method 3) has problems in that chemical resistance and scratch resistance are limited.

Therefore, suggested in U.S. Pat. No. 4,767,833 is a process for preparing transparent resin having superior impact resistance, chemical resistance, and processibility by graft copolymerizing styrene-butadiene rubber (SBR) latex with monomers such as methylmethacrylate, styrene, acrylonitrile, etc. in order to solve the problems. However, the method does not have good impact resistance at a low temperature, and it is limited in obtaining extremely superior transparent resin.
Furthermore, there are problems of deteriorated moisture and heat resistance in which products are discolored into a milky white color by hot water, and problems that products are discolored into a yellowish color by the influences of residual emulsifiers and coagulants remaining in the final products when the suggested technologies are applied to a product such as a transparent window of a washing machine, which has a great deal of contact with water.